Implement style invalidation tree walk for targeted style recalc upon class change.

Source/core/dom/shadow/SelectRuleFeatureSet.h

Index: Source/core/dom/shadow/SelectRuleFeatureSet.h
diff --git a/Source/core/dom/shadow/SelectRuleFeatureSet.h b/Source/core/dom/shadow/SelectRuleFeatureSet.h
index fd20c98e2de0fbabfd2a3d45df1916cf48cac62b..c9dfd2026061647bf8ed5fa147925a2d3df2912a 100644
--- a/Source/core/dom/shadow/SelectRuleFeatureSet.h
+++ b/Source/core/dom/shadow/SelectRuleFeatureSet.h
@@ -36,6 +36,9 @@
 
 namespace WebCore {
 
+class Element;
+class SpaceSplitString;
+
 class SelectRuleFeatureSet {
 public:
     SelectRuleFeatureSet();
@@ -58,6 +61,9 @@ public:
 
     bool hasSelectorFor(AffectedSelectorMask features) const { return m_featureFlags & features; }
 
+    bool checkSelectorsForClassChange(const SpaceSplitString& changedClasses) const;
+    bool checkSelectorsForClassChange(const SpaceSplitString& oldClasses, const SpaceSplitString& newClasses) const;
+
 private:
     void setSelectRuleFeature(AffectedSelectorType feature) { m_featureFlags |= feature; }